He denies murdering his 23-year-old stepson Dean Fitzpatrick outside his apartment at Northern Cross in Dublin in May 2013.
21 witnesses gave evidence over four days last week and the jury has been told it can also consider the lesser charge of manslaughter.
Mr. Mahon, who’s 45, is married to Dean’s mother Audrey and while he admits holding the knife that killed her son, he claims it was an accident.
On the opening day of the trial, the jurors heard Dean’s sister Amy hasn’t been seen since she went missing in Spain in 2008.
